Emotional State Classification from MUSIC-Based Features of Multichannel EEG Signals.

Electroencephalogram (EEG)-based emotion recognition is a computationally challenging issue in the field of medical data science that has interesting applications in cognitive state disclosure. Generally, EEG signals are classified from frequency-based features that are often extracted using non-parametric models such as Welch's power spectral density (PSD). These non-parametric methods are not computationally sound due to having complexity and extended run time. The main purpose of this work is to apply the multiple signal classification (MUSIC) model, a parametric-based frequency-spectrum-estimation technique to extract features from multichannel EEG signals for emotional state classification from the SEED dataset. The main challenge of using MUSIC in EEG feature extraction is to tune its parameters for getting the discriminative features from different classes, which is a significant contribution of this work. Another contribution is to show some flaws of this dataset for the first time that contributed to achieving high classification accuracy in previous research works. This work used MUSIC features to classify three emotional states and achieve 97% accuracy on average using an artificial neural network. The proposed MUSIC model optimizes a 95-96% run time compared with the conventional classical non-parametric technique (Welch's PSD) for feature extraction.

Avidin-Biotin Technology in Gold Nanoparticle-Decorated Graphene Field Effect Transistors for Detection of Biotinylated Macromolecules with Ultrahigh Sensitivity and Specificity.

The strong and specific noncovalent interaction between avidin and biotin is widely exploited in different types of enzyme-linked immunosorbent assay kits, labeled immunosensors, and polymer-based sensing devices for the detection of different biomarkers specific to different diseases such as cancer and influenza. Here, we employed the avidin-biotin technology in a novel gold nanoparticle-decorated graphene field-effect transistor (AuNP-GFET) and demonstrated the specific detection of the biotinylated macromolecules such as biotinylated proteins and nucleotides in the sub-picomolar (pM) range. The AuNP-GFET was constructed by fabricating six pairs of interdigital electrodes on graphene transferred on a SiO2/Si substrate. The sensing performance of AuNP-GFET was characterized by the real-time two-terminal electrical current measurement upon injection of the analyte solution into a silicone pool preattached onto the electrodes. Avidin, a tetrameric biotin-binding protein with strong affinity and specificity, immobilized on AuNP-decorated single-layer graphene, was used as the sensing platform and transduced the electrical signal upon binding to the analyte macromolecules. The sensing capability of the AuNP-GFET was tested with the biotinylated protein A. Sensitivity of the present biosensor was estimated to be ∼0.4 pM. The specificity and applicability of the biosensor were confirmed using both synthetic and real samples. Because the biotin label can retain its binding capability to avidin with strong affinity and specificity even after conjugating with varieties of proteins and nucleotides, the present AuNP-GFET biosensor is expected to promote the research in developing different biosensors.

Graphene field-effect transistor biosensor for detection of biotin with ultrahigh sensitivity and specificity.

Because avidin and biotin molecules exhibit the most specific and strongest non-covalent interaction, avidin-biotin technology is widely used in ELISA (enzyme-linked immunosorbent assay) kits for the detection of different bio-macromolecules linked to different diseases including cancer and influenza. Combining the outstanding electrical conductivity (200,000 cm2V-1s-1) of graphene with the unique avidin and biotin interaction, we demonstrate a novel graphene field-effect transistor (GFET) biosensor for the quantitative detection of bio-macromolecules. The GFET consists of six pairs of interdigital Cr/Au electrodes supported on Si/SiO2 substrate with an avidin immobilized single layer graphene channel as the sensing platform. By monitoring the real time current change upon the addition of biotin solution in bovine serum albumin (BSA) in the silicone pool preformed onto the GFET, the lowest detectable biotin concentration is estimated to be 90 fg/ml (0.37 pM). The specificity of the GFET is confirmed both by controlled and real sample measurements. From the magnitude of current change upon the addition of different concentrations of biotin solutions, the dissociation constant Kd is estimated to be 1.6 × 10-11 M. Since biotin is capable of conjugating with proteins, nucleotides and other bio-macromolecules without altering their properties, the present GFET sensor with its ultra-high sensitivity (0.37 pM) and specificity can be tailored to the rapid point-of-care detection of different types of desired biomolecules at very low concentration level through biotinylation as well as the exogenous biotin in blood serum.

Cholinesterase Inhibitor Therapy in Alzheimer's Disease: The Limits and Tolerability of Irreversible CNS-Selective Acetylcholinesterase Inhibition in Primates.

Irreversible acetylcholinesterase (AChE) inhibition accumulates to high levels in the central nervous system (CNS) because AChE turnover in the brain is much slower than in peripheral tissues. As expected from this CNS selectivity, the irreversible AChE inhibitor methanesulfonyl fluoride (MSF) produces significant cognitive improvement in Alzheimer's disease patients without the gastrointestinal toxicity that plagues other AChE inhibitors. However, without dose-limiting gastrointestinal toxicity, one shortcoming of the prior human studies of MSF is that the upper limits of CNS AChE inhibition that might be tolerated could not be tested. Therefore, in this study, monkeys were treated with escalating intramuscular (IM) doses of MSF that culminated with several weeks of 1.5 mg/kg dosing, more than eight times the prior human clinical dose, still without signs of toxicity. Brain biopsies showed that ∼80% AChE inhibition had been produced and that the new synthesis of cortical AChE had a half-time (t1/2) of ∼12 days. A single IM dose of 1.5 mg/kg MSF produced ∼59% inhibition in cerebrospinal fluid (CSF) AChE as measured one day later. This corresponds to a peak of ∼80% inhibition in CSF AChE at the time of the injection, recovering with a t1/2 of 2.4 days. Computational analyses suggest that MSF at clinically relevant doses could theoretically produce a steady-state AChE inhibition between 65% and 85% in the CNS. These data suggest that the full therapeutic advantage of AChE inhibition therapy can be realized without interference from dose-limiting gastrointestinal toxicity if an irreversible inhibitor is employed.

Measuring quality of sleep and autonomic nervous function in healthy Japanese women.

The purpose of this study was to determine the relationship between quality of sleep and autonomic nervous functioning in healthy adult Japanese women using three measures, namely, the Pittsburgh Sleep Quality Index (PSQI) for subjective assessment of sleep quality, actigraphy for objective assessment of sleep, and heart rate variability using high frequency and low frequency domains. Participants were 31 healthy women in their 20s to 40s who met the selection criteria, including having normal monthly menstrual periods. Participants were categorized as good or poor sleepers according to their PSQI score. Median correlation coefficients of activity count and high frequency were -0.62 (range -0.43 to -0.84) for good sleepers and -0.45 (range 0.003 to -0.64) for poor sleepers. Good sleepers showed a significantly higher correlation of activity count and high frequency (Z=-2.11, P<0.05). Median correlation coefficients of activity count and low frequency/high frequency were 0.54 (range 0.29-0.73) for good sleepers and 0.41 (range 0.11-0.63) for poor sleepers. The PSQI, actigraphy data, and heart rate variability results showed positive correlations between sleep time as measured by PSQI and duration of inactivity as measured by actigraphy (r=0.446, P<0.05) and sleep time as measured by actigraphy (r=0.377, P<0.05), and a negative correlation between sleep time as measured by PSQI and the correlation coefficients of activity count and high frequency (r=-0.460, P<0.01). These results support the finding that sleep-wake rhythms can be monitored efficiently with actigraphy, providing accurate data that can support the diagnosis of sleeping disorders. Furthermore, actigraphy data were associated with heart rate variability and PSQI findings, but only in subjects who were poor sleepers. Actigraphy is an accurate, efficient, rapid, and inexpensive test for determining objective and subjective sleeping problems, and can also be used in clinical tests for sleep assessment.

Acute effects of pyrethroids on serotonin release in the striatum of awake rats: an in vivo microdialysis study.

The present study examined the acute neurotoxic effects of three different pyrethroids, allethrin, cyhalothrin, and deltamethrin on the release of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of conscious rats using microdialysis. Allethrin 10 mg/kg reduced extracellular levels of 5-HT to 46%, whereas 20 and 60 mg/kg increased the release to 177% and 243% of baseline, respectively. Cyhalothrin increased 5-HT release to 145-204% and deltamethrin decreased to 58-32% of baseline in a dose-dependent manner. None of the pyrethroids tested altered extracellular levels of 5-HIAA. Local infusion of the voltage-gated sodium channel antagonist tetrodotoxin (TTX) into striatum completely prevented the effects of allethrin, cyhalothrin, and deltamethrin (10 and 20 mg/kg) on 5-HT release. The effect of deltamethrin at 60 mg/kg was completely abolished by striatal infusion of nimodipine (L-type Ca⁺⁺ channel antagonist) with TTX. These findings suggest that pyrethroids disrupt the serotonergic neurotransmission in striatum in a dose-related manner with Na⁺ and Ca²âº channel-dependent mechanisms.

Effect of a CNS-Sensitive Anticholinesterase Methane Sulfonyl Fluoride on Hippocampal Acetylcholine Release in Freely Moving Rats.

Anticholinesterases (antiChEs) are used to treat Alzheimer's disease. The comparative effects of two antiChEs, methanesulfonyl fluoride (MSF) and donepezil, on the extracellular levels of ACh in the hippocampus were investigated by in vivo microdialysis in freely moving rats. MSF at 1 and 2 mg/kg produced a dose-dependent increase in ACh efflux from 10 min to at least 3 hrs after injection. At 2 mg/kg, the increase was still present at 24 hr. Donepezil at 1 mg/kg showed a similar but smaller effect, and, paradoxically, 2 mg/kg showed no consistent effect. MSF at 1 and 2 mg/kg decreased acetylcholinesterase activity in the hippocampus to 54.8 and 20.1% of control, respectively. These results suggest that MSF is a suitable candidate for the treatment of Alzheimer's disease.

Effect of yoga on mental health: Comparative study between young and senior subjects in Japan.

BACKGROUND: Japan has a large number of senior citizens. Yoga can be wisely applied in old age care. There is no any age restriction to practice yoga. The effect may differ by age. There is a need to study the mechanism of action of yoga with respect to age. AIM: This study was conducted in Japan to find the effect of yoga on mental health between young and senior people. MATERIALS AND METHODS: Twenty-five normal healthy volunteers of both sexes were divided into two groups according to age. Fifteen participants of the age group between 65 to 75 years and 10 participants of the age group between 20 to 30 years were selected. This study was approved by the ethical committee of Kawasaki University of Medical Welfare. Selected individuals were subjected to 90 min of yoga classes once or twice a week for a month. Salivary amylase activity was assessed before and after yoga practice. State Trait Anxiety Inventory (STAI) was given before yoga on the first day and after one month of practice to assess the change in State anxiety and Trait anxiety. RESULTS: Senior group - Salivary amylase activity decreased from 111.2±42.7 to 83.48±39.5 kU/L [average±standard deviation]. Younger group - Salivary amylase activity reduced from 60.74±31.8 to 42.39±24 kU/L. Senior group - State anxiety score decreased from 41.13 ±8.43 to 30.8±6.49, Trait anxiety score reduced from 45.66±7.5 to 40.73±8.3. Younger group - State anxiety score reduced from 38.7±4.8 to 30.8±4.1,Trait anxiety score reduced from 46.2±7.9 to 42.9±9.1. Changes were statistically significant with P<0.05. CONCLUSION: Decrease in Salivary amylase activity may be due to reduction in sympathetic response. Reduction in State and Trait anxiety score signifies that yoga has both immediate as well as long-term effect on anxiety reduction. Thus yoga helps to improve the mental health in both the groups.

Tributyltin-induced Ca(2+) mobilization via L-type voltage-dependent Ca(2+) channels in PC12 cells.

The effects of tributyltin (TBT) on cytosolic Ca(2+) concentration ([Ca(2+)](c)) and cell viability were investigated in nerve growth factor-differentiated PC12 cells. TBT concentration dependently increased [Ca(2+)](c) with an EC(50) value of 0.07µM. This effect was markedly reduced by removal of the extracellular Ca(2+) or membrane depolarization with a high K(+) medium, but unaffected by thapsigargin causing depletion of intracellular Ca(2+) stores. The L-type voltage-dependent Ca(2+) channel (VDCC) blocker nicardipine blocked the effect of TBT, but the N-type VDCC blocker ω-conotoxin did not. TBT decreased the number of viable cells with an EC(50) value of 0.09µM. The TBT-induced cell death was prevented by nicardipine or by chelating the cytosolic Ca(2+) with BAPTA-AM, but not by ω-conotoxin. The results show that TBT causes an increase in [Ca(2+)](c) via activating L-type VDCCs, and support the idea that the organotin-induced cell death arises through Ca(2+) mobilization via L-type VDCCs.

Differential presynaptic actions of pyrethroid insecticides on glutamatergic and GABAergic neurons in the hippocampus.

This study was designed to investigate the effects of several pyrethroids on the extracellular level of glutamate and gamma-aminobutyric acid (GABA) in the hippocampus of rats measured using microdialysis following systemic (i.p.) administration. Pyrethroids, allethrin (type I), cyhalothrin (type II) and deltamethrin (type II), were found to have differential effects on glutamatergic and GABAergic neurons in the hippocampus. Allethrin had an interesting dual effect, increasing glutamate release with low doses (10 and 20mg/kg) to about 175-150% and decreasing glutamate release with high dose (60 mg/kg) to about 50% of baseline. Cyhalothrin (10, 20 and 60 mg/kg) inhibited the release of glutamate dose-dependently to about 60-30% of baseline. The extracellular level of GABA was decreased to about 50% of baseline by 10 and 20mg/kg allethrin. The high dose of allethrin (60 mg/kg) and all doses of cyhalothrin (10, 20 and 60 mg/kg) increased the extracellular level of GABA while decreasing the level of glutamate. Deltamethrin dose-dependently increased extracellular glutamate levels to about 190-275% of baseline while decreasing the level of GABA. Local infusion of TTX (1 microM), a Na(+) channel blocker, completely prevented the effect of allethrin (10, 20 and 60 mg/kg), cyhalothrin (20 and 60 mg/kg) and deltamethrin (20mg/kg) on glutamate and GABA release, but only partially blocked the effects of 60 mg/kg deltamethrin. The effect of deltamethrin (60 mg/kg) on glutamate release was completely prevented by local infusion of nimodipine (10 microM), an L-type Ca(2+) channel blocker. Collectively, results from this study suggest that the excitatory glutamatergic neurons in the hippocampus are modulated by inhibitory GABA-releasing interneurons and that other mechanisms, beside sodium channels, may be involved with the neurotoxic action of pyrethroids.

Key role of mucosal primary afferents in mediating the inhibitory influence of capsaicin on vagally mediated contractions in the mouse esophagus.

Transient receptor potential ion channel of the vanilloid type 1 (TRPV1)-dependent pathway, consisting of capsaicin-sensitive tachykininergic primary afferent and myenteric nitrergic neurons, was suggested to mediate the inhibitory effect of capsaicin on the vagally mediated striated muscle contractions in the rat esophagus. These primary afferent neurons upon entering into the esophagus are distributed through the myenteric plexus, terminating either in the myenteric ganglia or en route to the mucosa where they branch into a delicate net of fine varicose fibers. Therefore, this study aimed to investigate whether the mucosal primary afferents are a main mediator for the capsaicin inhibitory influence on vagally mediated contractions in the mouse esophagus. For this purpose, the vagally induced contractile activity of a thoracic esophageal segment was measured in the circular direction with a force transducer. Vagal stimulation (30 microsec, 25 V, 1-50 Hz for 1 sec) produced monophasic contractile responses, whose amplitudes were frequency-dependent. These contractions were completely abolished by d-tubocurarine (5 microM) while resistant to atropine (1 microM) and hexamethonium (100 microM). Capsaicin (30 microM) significantly inhibited the vagally induced contractions in esophagi with intact mucosa while its effect on preparations without mucosa was insignificant. Additionally, immunocytochemistry revealed the presence of TRPV1-positive nerve fibers in the tunica mucosa. Taken together, we conclude that in the mouse esophagus, capsaicin inhibits the vagally mediated striated muscle contractions mainly through its action on mucosal primary afferents, which in turn activate the presumed inhibitory local reflex arc.

Involvement of TRPV1-dependent and -independent components in the regulation of vagally induced contractions in the mouse esophagus.

Transient receptor potential ion channel of the vanilloid type 1 (TRPV1)-dependent pathway, consisting of capsaicin-sensitive tachykininergic primary afferent and myenteric nitrergic neurons, has been suggested to mediate the inhibitory effect of capsaicin on vagally mediated striated muscle contractions in the rat esophagus. In a recent study, similar but also different effects of capsaicin and piperine on TRPV1 were demonstrated. Therefore, this study aimed to compare the effects of these two drugs on vagally induced contractions in the mouse esophagus. Capsaicin and piperine inhibited vagally induced contractions of a thoracic esophageal segment in a concentration-dependent manner. Ruthenium red (10 microM; a non-selective blocker of transient receptor potential cation channels) and SB-366791 (10 microM; a novel selective antagonist of TRPV1) blocked the inhibitory effect of capsaicin but not that of piperine. Piperine inhibited the vagally mediated contractions in esophagi of adult mice neonatally injected with capsaicin, while capsaicin failed to do so. Desensitization of TRPV1 in the mouse esophagus by in vitro pretreatment with capsaicin failed to affect the inhibitory effect of piperine, whereas the piperine effect was cross-desensitized by capsaicin pretreatment in rat and hamster esophagi. Additionally, a tachykinin NK(1) receptor antagonist, L-732,138 (1 microM), as well as a nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME 200 microM), blocked the inhibitory effect of capsaicin but not that of piperine. Taken together, the results suggest that piperine inhibits the vagally mediated striated muscle contraction in the mouse esophagus through its action on a TRPV1-dependent pathway as well as a TRPV1-independent site.

Brain regional acetylcholinesterase activity and muscarinic acetylcholine receptors in rats after repeated administration of cholinesterase inhibitors and its withdrawal.

Activity of acetylcholinesterase (AChE) and specific binding of [(3)H]quinuclidinyl benzilate (QNB), [(3)H]pirenzepine (PZP) and [(3)H]AF-DX 384 to muscarinic acetylcholine receptor (mAChR) preparations in the striatum, hippocampus and cortex of rats were determined 1, 6 and 11 days after the last treatment with an organophosphate DDVP, a carbamate propoxur or a muscarinic agonist oxotremorine as a reference for 7 and 14 days. AChE activity was markedly decreased in the three regions 1 day after the treatment with DDVP for 7 and 14 days with a gradual recovery 6 to 11 days, and much less decreased 1, 6 and 11 days after the treatment with propoxur for 7 days but not for 14 days in the hippocampus and cortex. The binding of [(3)H]-QNB, PZP and AF-DX 384 in the three regions was generally decreased by the treatment with DDVP for 7 and 14 days. Such down-regulations were generally restored 6 or 11 days after the treatment for 7 but not for 14 days. The down-regulation or up-regulation as measured by [(3)H]-QNB, PZP and AF-DX 384 was observed 1, 6 or 11 days after treatment with propoxur for 7 days and/or 14 days. Repeated treatment with oxotremorine produced similar effects except AChE activity to DDVP. These results suggest that repeated inhibition of AChE activity may usually cause down-regulation of mAChRs with some exception in the hippocampus when a reversible antiChE propoxur is injected.

Effects of formalin-preservation on element concentrations in animal tissues.

Determination of the exposure level of environmental pollutants is essential in studies on environmental toxicology. If concentrations of exposed pollutants in tissues are not affected by formalin-preservation, a preserved specimen will provide not only histopathological information but also the exposure level of environmental pollutants. In the present study, concentrations of nine elements in the liver and kidney were compared between fresh and formalin- or neutral formalin-preserved specimens to validate the ultimate analysis of the preserved specimens. After one year of preservation, various elements had diffused from the specimens into the solutions. The concentrations of iron, copper, zinc (in the case of neutral formalin) and selenium in the central region of the specimens showed no alterations, suggesting that the diffusions of these elements were limited to the surface of the specimens. Therefore, preserved specimens may be available for the determination of these elements if the specimens are large enough for their surface to be removed. Concentrations of other elements in the preserved specimens were different from the original ones, because the diffusion or infiltration also occurred in the deep region of the specimens.

Differential effects of pyrethroid insecticides on extracellular dopamine in the striatum of freely moving rats.

In order to obtain a more complete understanding of pyrethroid neurotoxicity, effects of the pyrethroid insecticides, allethrin (type I), cyhalothrin (type II) and deltamethrin (type II) on extracellular levels of dopamine (DA) and its metabolites in the striatum of conscious rats were studied by in vivo microdialysis. Rats were treated i.p. with pyrethroids or vehicle. Allethrin had a dual effect on DA release. The increase in the extracellular level of striatal DA by 10 mg/kg allethrin reached a maximum of 178% of baseline but 20 and 60 mg/kg inhibited DA release to 63% and 52% of baseline with a peak effect at 60-80 min after injection. Cyhalothrin 10, 20 and 60 mg/kg inhibited DA release to 65%, 56% and 45% of basal release, respectively, with a peak time of inhibition 40-80 min past injection. Deltamethrin (10 and 20 mg/kg) increased DA release to maximum of 187% and 252% of basal release whereas 60 mg/kg first reduced the efflux for 40 min to 50% of basal release and then increased the efflux to a maximum of 344% of basal release with a peak time of 120 min. Local infusion of 1 microM tetrodotoxin, a Na(+) blocker through the dialysis probe completely prevented the effect of allethrin (10 and 60 mg/kg), cyhalothrin (60 mg/kg) and deltamethrin (20 mg/kg) on DA release but only partially blocked the effects of 60 mg/kg deltamethrin. The effect of deltamethrin (60 mg/kg) on DA release was completely prevented by local infusion of 10 microM nimodipine, an L-type Ca(++) channel blocker. All three pyrethroids did not alter the extracellular levels of DOPAC, 3-MT and HVA except that 20 and 60 mg/kg of allethrin and cyhalothrin increased 3-MT levels. Effect of the pyrethroids on synaptosomal DA uptake was also examined. The DA uptake was decreased in rats exposed to 60 mg/kg of allethrin and cyhalothrin but was increased in rats exposed to 60 mg/kg of deltamethrin. Our results demonstrate that striatal DA release and DA uptake are differentially affected by type I and the two type II pyrethroids indicating that dopaminergic circuitry, striatal DA in particular, may be a pyrethroid target and that pyrethroids may be acting on striatal DA by multiple mechanisms.

Antiinflammatory effect of Japanese horse chestnut (Aesculus turbinata) seeds.

The antiinflammatory effects of Japanese horse chestnut (Aesculus turbinata) seeds were examined in vivo and in vitro. The extract of this seed (HCSE) inhibited croton oil-induced swelling of the mouse concha. HCSE inhibited cyclooxygenase (COX) -1 and -2 activities, but had no effect on 15-lipoxygenase and phospholipase A2 activities. Inhibition of COX-2 occurred at a lower concentration of HCSE than for COX-1. Japanese horse chestnut seeds contain coumarins and saponins, but these chemicals did not inhibit COX activities. These results suggest that the antiinflammatory effect of Japanese horse chestnut seeds is caused, at least partly, by the inhibition of COX. The inhibitor of COX in this seed may be a chemical(s) other than coumarins and saponins.

Antioxidative and antigenotoxic effects of Japanese horse chestnut (Aesculus turbinata) seeds.

Japanese horse chestnut seed extract (HCSE) dose-dependently inhibited the autooxidation of linoleic acid (IC(50): 0.2 mg/ml), and the inhibition was almost complete at a concentration of 1 mg/ml. The HCSE scavenged DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals and superoxide anions with EC(50)s of 0.65 and 0.21 mg/ml, respectively. However, it had no effect on hydrogen peroxide. The HCSE inhibited the genotoxicities of furylfuramide, N-methyl-N-nitrosourea, methyl methanesulfonate, mitomycin C, 2-aminoanthracene and aflatoxin B1 at a concentration of 1 mg/ml or more. Total polyphenol content of the HCSE was 21 mg/g (13 mg/g-seeds). These results indicate that the Japanese horse chestnut seed is an antioxidative and antimutagenic botanical resource.

Neuromechanical effects of pyrethroids, allethrin, cyhalothrin and deltamethrin on the cholinergic processes in rat brain.

Our previous microdialysis study of freely moving rats demonstrated that 3 pyrethroids, allethrin (type I), cyhalothrin (type II) and deltamethrin (type II) differentially modulate acetylcholine (ACh) release in the hippocampus. To better understand the mechanisms of their modulatory effects and also other effects on the cholinergic system in the brain, the activities of ACh hydrolyzing enzyme acetylcholinesterase (AChE), ACh synthesizing enzyme choline acetyltransferase (ChAT) and ACh synthesizing rate-limiting step, high-affinity choline uptake (HACU) were examined in the present study. The pyrethroids studied had no effect on AChE activity in the cortex, hippocampus and striatum. These pyrethroids had no significant effect on ChAT in the cortex and hippocampus, but striatal ChAT was increased at higher dosage (60 mg/kg) by all three compounds. Lineweaver-Burk analysis of hippocampal HACU revealed that the pyrethroids did not alter the Michaelis-Menten constant (Km) value but caused alteration of maximal velocity (Vmax). Allethrin (60 mg/kg) and cyhalothrin (20 and 60 mg/kg) decreased while deltamethrin (60 mg/kg) increased the Vmax for HACU. In vitro study showed that at higher concentrations (> or = 10(-) (6) M) allethrin and cyhalothrin reduced the hippocampal HACU but deltamethrin increased it. These results suggest that mechanisms of ACh synthesis are involved in the modulatory effects of the pyrethroids on ACh release and other cholinergic activities.